It is known that high-polymer hydroxycarboxylic acids such as polylactide and polyglycolide are biocompatible and have high compatibility with the body, so that for a rather long time, they have already been used in surgery, as slow-resorbing sutures or as osteosynthetic implants. These high-polymer polycarboxylic acids break down over weeks or months and are broken down by the human or animal body in the usual way via the citric acid cycle or lipometabolism. For this reason, such polymers can also be unobjectionably used as osteosynthetic implants, for example, and in that case they also have the advantage that a second operation for removing the implants is no longer necessary, or is only necessary for the part of the implant that is not of polymer.
From German Published, Non-Examined Patent Application DE-OS 36 20 685, means based on free-flowing to solid oligomeric esters of lactic acid and/or glycolic acid for covering uninjured and/or injured human or animal skin are also known. These preparations substantially comprise the oligomeric esters as resorbable vehicles or film formers and can additionally contain skin-care agents and regenerating, disinfecting, or epithelium-stimulating substances. Film-forming polymers of lactic acid and glycolic acid in solvents such as ethyl acetate, which in addition contain pharmacological active ingredients and can for instance be used as a sprayed-on bandage, are also known from French Patent Application 21 26 270.
From U.S. Pat. Nos. 4,045,418 or 4,148,871, copolymers of lactide and .epsilon.-caprolactone are also known, which are biocompatible and can for instance be used as subdermally implantable containers for medications. The compatibility and biodegradability of such containers has been reported, for instance in the Journal of Biomedical Materials Research, Vol. 13, pp. 497-507, 1979 and in Naltrexone: Research Monograph 28, National Institute on Drug Abuse, 1983, written by the team of Colin G. Pitt et al.
A disadvantage of previously known mono- and copolymers of lactic acid and glycolic acid is the fact that they are compounds that are as a rule applied in solutions and are intrinsically relatively hard and not very flexible, so that such sprayed-on films rapidly become brittle and crack after the solvent has evaporated; a further factor is that they do not adhere very well to the surface of the skin or of a wound. On the other hand, as a rule, the previously used polymers of lactide and .epsilon.-caprolactone are stiff thermoplastics, suitable for producing containers, for instance, but not for topical application.
Accordingly, there is still a need for biocompatible polymers that can be used on the skin and that do not have the aforementioned disadvantages.